"I always heard the duramax 6.6/Allison trans was a reliable bulletproof combo. I’m finding out that I should of kept my 6.5TD and my hummer H1. My GMC Sierra blew head gasket at 108k miles after 5 recalls . The dealer put a “new engine” in it which means they ordered a new engine block and transferred all the old parts onto it. I picked up my truck today after waiting almost 5 months for the factory to release it. I was hoping that it would be in great running condition but I picked it up, started driving home and not only did my engine light come on but thank god I stopped to refuel and check all the fluids because the engine oil was 1/2 gallon low and the antifreeze reservoir was almost empty (low level light went on). I drove two hours home slowly making sure not to overheat the engine. Now I have to wait till Monday to see what needs to be done after paying 10k dollars plus for the work. I’m hoping the old injectors are not on the new block because it would of been so easy to replace them with the engine removed, they usually malfunction soon after 108k miles and I’m not looking forward to adding 5k to the pile.
My experience with the diesel combo, go with a gasser. Not worth the aggravation and extra cost. This truck has been a nightmare and I should of taken it to a duramax specialist that works on these engines on a regular basis. Not the dealership. My suggestion, stay away from the diesel unless you plan to tow a lot and have deep pockets."